To manage these settings, click your Account Name and select Settings from the dropdown menu.

Click Research from the left menu.

You can not only select what a Great Rank is to you, but you can do so on the individual category level, as well as change the total items in a category.

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The category list is scrollable on the left side.

The fields for the Total Items and A Great Rank Is are editable so you can update those whenever you get new information.

The far-right column automatically calculates the Great Rank number based on the Total and the Rank percentage you enter.